Hello. I am wondering if this is an active site - I hope so. I have a small vase with a ruffled top opening, an abstract painting method, paintings of clumps of plants/grasses - one on each side and in gold, a translucent bottom and a Rosenthal backstamp with no indication of any other identifier. All the marks I've seen have information below the lion, crown, Rosenthal name separated by the X, and the flourish of the line below the whole name/word. I'm sure its a stamp. It's a little skewed because of the curvature of the bottom of the base. It is very close to 5" tall and the diameter is 9.5" near the top and just under 8" near the bottom. If I need to provide any more information, please tell me.
I don't see any other Rosenthal vase or any piece for that matter painted this splochy abstract way. I hope someone who knows much more than me will see this.
I'm not an expert in Rosenthal marks. However, eBay hosts a Pottery, Glass, & Porcelain Discussion Board where you may post pictures of your item and its mark, and there are members there who can help you. Also, you can check your mark against those at one of the PGP members' site for German marks, at Porcelain Marks & More. Good luck!